I. Field of the Invention
This invention is directed generally to a video surveillance system for monitoring a continuous web, such as a web of paper navigating through the many rolls of a paper machine from the head box at the wet end or formation section to the dry end. More particularly, the invention relates to an integrated video surveillance system using multiple cameras and multiple video screens to display, record and playback the operation at critical points in the machine such that, upon the occurrence of a failure or break in the web, the system can automatically or manually replay events recorded just prior to the break to aid in determining the cause of the web failure.
II. Description of the Related Art
The making of paper includes the passing of a long, continuous web of material over a plurality of rolls in continuous form. The web is formed from a heated slurry of bleached pulp fibers, starch, clay and other additives containing about one part bleached fibers and additives combined with 99 parts water. The slurry is received as furnish from the head box between two endless wire screens and formed into a relatively wide uniform sheet which is thereafter squeeze dried between a plurality of heavy rollers and eventually wound on reels in the form of large paper rolls which may be cut to any desired length and width. The continuous web may have a width approaching 25 feet and be many hundreds of feet long. The forming process utilizes both heat and pressure to form a relatively thick, slow moving mass into what may be a very thin layer of dry paper moving at high speed as it is wound on large spindles at the exit end of the paper machine. During this process, the continuous web encompasses a variety of types of rollers and tension control devices. These include initial heated drying drums, drum rollers, thickness reduction rollers, and, in the case of high-gloss papers, super calender rollers which "iron" the paper between hard steel rollers and roller covers with more resilient coverings.
It is apparent that a process where a continuous web of material such as paper is being processed as a single continuous length of material beginning at its formation from a slurry through its polished, highly finished condition in roll form, the integrity of the web is critical to the continued operation of the process. Because defects and imperfections in the web do occur from time to time, and because such devices as those controlling web tension, for example, sometimes get out of calibration, web failures occur. In addition, with the exception of the very beginning of a formation of the paper web in the wet end of the paper machine, the web itself moves quite rapidly such that by the time the dried web of final thickness is reached, the speed of the web of material moving through the process is extremely rapid, reaching as much as 100 feet per second. Thus, when a break in the web does occur, it happens very rapidly and, even if viewed in real-time, the cause often is not apparent. Thereafter it may be extremely difficult to determine the exact cause of the web failure. While devices exist which monitor the continuity of the continuous web and which operate to shut down the machinery quickly should breakage or discontinuity occur, such devices do not aid in determining the cause of web failure.
Systems for inspecting and characterizing continuous webs of material later for defects including providing video recordings of the passage of a continuous web of materials such as paper are known. One such system records the passage of a continuous web of paper on videotape which can subsequently be replayed and inspected thereby allowing inspection of the material to be carried out separately from the real-time material processing. This system is disclosed in Wales et al. (U.S. Pat. No. 4,951,223). Another monitoring system is shown in Pajunan (U.S. Pat. No. 4,918,422). Further multi-camera video surveillance systems are disclosed in Oliver, Jr. (U.S. Pat. No. 4,814,869) and Williams (U.S. Pat. 4,581,634).
Each time the paper web fails, the paper making machine must be stopped while the cause of the breakage is determined, any necessary equipment repairs made and the continuous web rethreaded so that the machine can resume operation. Such "down time" is very expensive as the entire process comes to a standstill. Minimizing down time is a very important consideration in any such continuous operation. Early diagnosis of the cause of the breakage or failure may be critical with respect to the time it takes to conduct any necessary repairs and restore the line to full operation. Therefore, a system which enables the operator to determine the cause of the failure more rapidly could provide invaluable information with respect to conducting any necessary repairs.
A surveillance system which can monitor the continuous web of a paper making machine in a manner such that when breaks occur, the interval just prior to the break can be automatically replayed to determine the probable cause of the web failure has remained a definite need with respect to the operation of paper machines. It would be a great advantage to have a multi-camera surveillance system which could react to breaks in the continuous paper web in a manner which would facilitate diagnosis of the cause of the web failure in a manner such that the cause can be diagnosed and the system corrected in the shortest possible time.